This project is designed to study the interaction between electrical and mechanical stimuli in stimulated bone formation at implants. Previous work has suggested that mechanical factors may be responsible for, or contribute to, electrically stimulated osteogenesis in both animal experiments and clinical application to fracture healing. As part of a rational search for mechanisms for this controversial methodology, the existence of such a relationship should first be confirmed or denied and its nature determined. A well-accepted, direct current cathode/rabbit implant model will be used. Small, calibrated intermittent mechanical forces will be introduced to the implants by means of external magnetic fields attracting a ferromagnetic core material. The medullary osteogenic response will be measured from histologic sections in terms of new bone mass, cartilage growth, etc. The applied force will be varied over a reasonable range and the duration of application varied. Frequency (rate) of pulsed forces will also be studied. Implants with and without current, and with and without mechanical stimulus will be used along with 2 different, but proven, cathode electrode systems. If a dependent relationship is found between electrical and mechanical stimuli in bone formation at the implant, a re-evaluation of the effectiveness of "electrical" methods may be indicated. Perhaps a more important output of this study would be new information on the biophysical mechanisms of stimulated osteogenesis, bone remodeling and Wolff's law.